The present invention relates generally to load monitoring systems, and more particularly, to systems for monitoring and controlling loads incurred by force carrying members, such as pitmans of production presses.
Load monitoring systems are known at present for indicating the loads on presses and for automatically detecting if the load incurred by the force carrying member exceeds a predetermined value or is below a predetermined value. Systems, such as shown in the applicant's U.S. Pat. No. 4,062,055, have been found to be highly valuable in controlling costly overload breakdowns and detecting production line delays resulting from the failure of a workpiece to be loaded into the press at the appropriate time. Such systems in general provide a transducer attached to the force carrying member of the press which generates an electrical load signal substantially proportional to the load exerted on the force carrying member. In addition such systems provide a high load limit circuit and a low load limit circuit which respectively determine whether the load signal exceeds a predetermined value (an overload) or is below a predetermined value (an underload). As set forth in greater detail in U.S. Pat. No. 4,062,055, the ability to detect an overload and an underload of the press provides significant advantages in controlling the production of the press.
For the stamping or punching of intricate parts in a press, it is common to use a progressive die having a plurality of individual die stations which are effectively active only at certain phases in the press cycle. A progressive die, in other words, is somewhat equivalent to a plurality of individual dies driven by a common press. The system as shown in U.S. Pat. No. 4,062,055, however, cannot independently monitor each of the die stations in the progressive die, since it is responsive to the maximum load during the entire cycle and the failure of a minimum load to be achieved in the press cycle.